There’s a bit of a slip from the gearbox
Q From time to time my BMC 1800 engine with PRM gearbox suffers from little or no forward drive. Selecting and revving in reverse, then selecting forward seems to rectify the problem? At the last service during 2016 I mentioned this issue, but was advised it was because ‘the oil was past its best’ and simply needed changing. All appeared good for several months, but it has begun to happen again. Any thoughts? VIC GORNY, via email A TONY REPLIES: A hydraulic gearbox will do this if it is short of oil or is not correctly filled with engine oil, rather than thin red ATF/Dexron as used in some other makes. Remove the cable from the operating lever on the gearbox and put it in and out of gear by hand. If that solves the problem, adjust the cable. If you have no gearbox oil cooler, the oil may be overheating and getting too thin. If none of the above solves the problem, the ahead clutch might be slipping. But before jumping to that conclusion get the gearbox hot oil pressure tested, because a worn pump or blocked internal oil strainer would cause low oil pressure and clutch slip.